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[linuxjm/LDP_man-pages.git] / draft / man2 / truncate.2

.\" Copyright (c) 1983, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"     This product includes software developed by the University of
.\"     California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)truncate.2  6.9 (Berkeley) 3/10/91
.\"
.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
.\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 1998-12-21 by Andries Brouwer <aeb@cwi.nl>
.\" Modified 2002-01-07 by Michael Kerrisk <mtk.manpages@gmail.com>
.\" Modified 2002-04-06 by Andries Brouwer <aeb@cwi.nl>
.\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" Japanese Version Copyright (c) 1997 SUTO, Mitsuaki
.\"         all rights reserved.
.\" Translated 1997-06-26, SUTO, Mitsuaki <suto@av.crl.sony.co.jp>
.\" Modified 2000-03-12, HANATAKA Shinya <hanataka@abyss.rim.or.jp>
.\" Updated 2001-01-09, Kentaro Shirakata <argrath@ub32.org>
.\" Updated 2002-04-13, Kentaro Shirakata <argrath@ub32.org>
.\" Updated 2002-10-21, Kentaro Shirakata <argrath@ub32.org>
.\" Updated 2005-09-06, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\" Updated 2006-07-21, Akihiro MOTOKI, LDP v2.36
.\"
.TH TRUNCATE 2 2009-02-28 "Linux" "Linux Programmer's Manual"
.\"O .SH NAME
.SH ̾Á°
.\"O truncate, ftruncate \- truncate a file to a specified length
truncate, ftruncate \- »ØÄꤷ¤¿Ä¹¤µ¤Ë¥Õ¥¡¥¤¥ë¤òÀÚ¤êµÍ¤á¤ë
.\"O .SH SYNOPSIS
.SH ½ñ¼°
.B #include <unistd.h>
.br
.B #include <sys/types.h>
.sp
.BI "int truncate(const char *" path ", off_t " length );
.br
.BI "int ftruncate(int " fd ", off_t " length );
.sp
.in -4n
.\"O Feature Test Macro Requirements for glibc (see
.\"O .BR feature_test_macros (7)):
glibc ¸þ¤±¤Îµ¡Ç½¸¡ºº¥Þ¥¯¥í¤ÎÍ×·ï
.RB ( feature_test_macros (7)
»²¾È):
.in
.ad l
.sp
.BR truncate ():
_BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500
.br
.BR ftruncate ():
_BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 || _POSIX_C_SOURCE\ >=\ 200112L
.ad b
.\"O .SH DESCRIPTION
.SH ÀâÌÀ
.\"O The
.\"O .BR truncate ()
.\"O and
.\"O .BR ftruncate ()
.\"O functions cause the regular file named by
.\"O .I path
.\"O or referenced by
.\"O .I fd
.\"O to be truncated to a size of precisely
.\"O .I length
.\"O bytes.
.\"O If the file previously was larger than this size, the extra data is lost.
.BR truncate ()
¤Ï
.I path
¤Ç»ØÄꤵ¤ì¤ë¥Õ¥¡¥¤¥ë¤ò¡¢
.BR ftruncate ()
¤Ï
.I fd
¤Ç»²¾È¤µ¤ì¤ë¥Õ¥¡¥¤¥ë¤ò
.I length
¥Ð¥¤¥È¤ÎŤµ¤Ë¤Ê¤ë¤è¤¦¤Ë±äŤ¹¤ë¡¢¤â¤·¤¯¤ÏÀÚ¤êµÍ¤á¤ë¡£
¤â¤·ÀÚ¤êµÍ¤á¤ëÁ°¤Î¥Õ¥¡¥¤¥ë¤¬
.I length
¤è¤êŤ±¤ì¤Ð¡¢length ¥Ð¥¤¥È¤ò±Û¤¨¤ëÉôʬ¤Î¥Ç¡¼¥¿¤Ï¼º¤ï¤ì¤ë¡£
.\"O If the file previously was shorter, it is extended, and
.\"O the extended part reads as null bytes (\(aq\\0\(aq).
¤â¤·ÀÚ¤êµÍ¤á¤ëÁ°¤Î¥Õ¥¡¥¤¥ë¤¬
.I length
¤è¤êû¤«¤±¤ì¤Ð¡¢¿­Ä¥¤µ¤ì¤ë¡£
¿­Ä¥¤µ¤ì¤¿Éôʬ¤òÆɤó¤À¾ì¹ç¤Ï NULL ¥Ð¥¤¥È (\(aq\\0\(aq) ¤ÎÎó¤¬ÊÖ¤µ¤ì¤ë¡£
.LP
.\"O The file offset is not changed.
¥Õ¥¡¥¤¥ë¥ª¥Õ¥»¥Ã¥È¤ÏÊѹ¹¤µ¤ì¤Ê¤¤¡£
.LP
.\"O If the size changed, then the st_ctime and st_mtime fields
.\"O (respectively, time of last status change and
.\"O time of last modification; see
.\"O .BR stat (2))
.\"O for the file are updated,
.\"O and the set-user-ID and set-group-ID permission bits may be cleared.
Â礭¤µ¤¬Êѹ¹¤µ¤ì¤ë¤È¡¢¥Õ¥¡¥¤¥ë¤Î st_ctime ¤È st_mtime ¥Õ¥£¡¼¥ë¥É
(¤½¤ì¤¾¤ìºÇ½ª¾õÂÖÊѹ¹»þ¹ï¡¢ºÇ½ª½¤Àµ»þ¹ï;
.BR stat (2)
»²¾È) ¤¬¹¹¿·¤µ¤ì¤ë¡£
¤Þ¤¿¡¢set-user-ID ¤È set-group-ID ¤Îµö²Ä¥Ó¥Ã¥È¤¬¥¯¥ê¥¢¤µ¤ì¤ë¤«¤â¤·¤ì¤Ê¤¤¡£
.LP
.\"O With
.\"O .BR ftruncate (),
.\"O the file must be open for writing; with
.\"O .BR truncate (),
.\"O the file must be writable.
.BR ftruncate ()
¤Î¾ì¹ç¡¢¥Õ¥¡¥¤¥ë¤Ï½ñ¤­¹þ¤ßÍѤ˳«¤¤¤Æ¤¤¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£
.BR truncate ()
¤Î¾ì¹ç¡¢¥Õ¥¡¥¤¥ë¤Ï½ñ¤­¹þ¤ß²Äǽ¤Ç¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£
.\"O .SH "RETURN VALUE"
.SH ÊÖ¤êÃÍ
.\"O On success, zero is returned.
.\"O On error, \-1 is returned, and
.\"O .I errno
.\"O is set appropriately.
À®¸ù¤·¤¿¾ì¹ç 0 ¤¬Ê֤롣¼ºÇÔ¤·¤¿¾ì¹ç \-1 ¤¬Ê֤ꡢ
.I errno
¤¬¥¨¥é¡¼¤ÎÆâÍƤ˽¾¤Ã¤ÆÀßÄꤵ¤ì¤ë¡£
.\"O .SH ERRORS
.SH ¥¨¥é¡¼
.\"O For
.\"O .BR truncate ():
.BR truncate ()
¤Ç¤Ï°Ê²¼¤Î¥¨¥é¡¼¥³¡¼¥É¤¬ÄêµÁ¤µ¤ì¤Æ¤¤¤ë¡£
.TP
.B EACCES
.\"O Search permission is denied for a component of the path prefix,
.\"O or the named file is not writable by the user.
.\"O (See also
.\"O .BR path_resolution (7).)
¥Ñ¥¹¤Ç»ØÄꤵ¤ì¤Æ¤¤¤ë¥Ç¥£¥ì¥¯¥È¥ê¤Ë¸¡º÷µö²Ä¤Î¤Ê¤¤¤â¤Î¤¬¤¢¤ë
(ÌõÃí:x ¥Ó¥Ã¥È¤¬Î©¤Ã¤Æ¤¤¤Ê¤¤)¡£
¤¢¤ë¤¤¤Ï¡¢»ØÄꤵ¤ì¤¿¥Õ¥¡¥¤¥ë¤ËÂФ¹¤ë½ñ¤­¹þ¤ßµö²Ä¤ò»ý¤Ã¤Æ¤¤¤Ê¤¤¡£
.RB ( path_resolution (7)
¤â»²¾È¤Î¤³¤È)
.TP
.B EFAULT
.\"O .I Path
.\"O points outside the process's allocated address space.
.I path
¤¬¥×¥í¥»¥¹¤Ë³ä¤êÅö¤Æ¤é¤ì¤Æ¤¤¤ë¥¢¥É¥ì¥¹¶õ´Ö³°¤ò»Ø¤·¤Æ¤¤¤ë¡£
.TP
.B EFBIG
.\"O The argument
.\"O .I length
.\"O is larger than the maximum file size. (XSI)
°ú¤­¿ô
.I length
¤¬ºÇÂç¥Õ¥¡¥¤¥ë¥µ¥¤¥º¤è¤êÂ礭¤¤¡£(XSI)
.TP
.B EINTR
.\"O A signal was caught during execution.
¼Â¹ÔÃæ¤Ë¥·¥°¥Ê¥ë¤ò¼õ¤±¤¿¡£
.TP
.B EINVAL
.\"O The argument
.\"O .I length
.\"O is negative or larger than the maximum file size.
°ú¤­¿ô
.I length
¤¬Éé¿ô¤Ç¤¢¤ë¤«¡¢ºÇÂç¥Õ¥¡¥¤¥ë¥µ¥¤¥º¤è¤êÂ礭¤¤¡£
.TP
.B EIO
.\"O An I/O error occurred updating the inode.
inode ¤Î¹¹¿·»þ¤Ë I/O ¥¨¥é¡¼¤¬È¯À¸¤·¤¿¡£
.TP
.B EINTR
.\"O While blocked waiting to complete,
.\"O the call was interrupted by a signal handler; see
.\"O .BR fcntl (2)
.\"O and
.\"O .BR signal (7).
´°Î»ÂÔ¤Á¤ÇÄä»ß (block) ¤·¤Æ¤¤¤ë´Ö¤Ë¡¢¸Æ¤Ó½Ð¤·¤¬
¥·¥°¥Ê¥ë¥Ï¥ó¥É¥é¤Ë¤è¤ê³ä¤ê¹þ¤Þ¤ì¤¿¡£
.BR fcntl (2)
¤È
.BR signal (7)
¤ò»²¾È¡£
.TP
.B EISDIR
.\"O The named file is a directory.
»ØÄꤵ¤ì¤¿¥Õ¥¡¥¤¥ë¤Ï¥Ç¥£¥ì¥¯¥È¥ê¤Ç¤¢¤ë¡£
.TP
.B ELOOP
.\"O Too many symbolic links were encountered in translating the pathname.
¥Ñ¥¹Ì¾¤ò²ò¼á¤¹¤ëºÝ¤Ë¥·¥ó¥Ü¥ê¥Ã¥¯¥ê¥ó¥¯¤¬Â¿¤¹¤®¤¿¡£
.TP
.B ENAMETOOLONG
.\"O A component of a pathname exceeded 255 characters,
.\"O or an entire pathname exceeded 1023 characters.
¥Ñ¥¹Ì¾Ãæ¤Î¥Ç¥£¥ì¥¯¥È¥ê̾¤¬ 255 ʸ»ú¤ò±Û¤¨¤Æ¤¤¤ë¡¢¤â¤·¤¯¤Ï¥Ñ¥¹Ì¾Á´ÂΤ¬
1023 ʸ»ú¤ò±Û¤¨¤Æ¤¤¤ë¡£
.TP
.B ENOENT
.\"O The named file does not exist.
»ØÄꤵ¤ì¤¿Ì¾Á°¤Î¥Õ¥¡¥¤¥ë¤¬Â¸ºß¤·¤Ê¤¤¡£
.TP
.B ENOTDIR
.\"O A component of the path prefix is not a directory.
¥Ñ¥¹Ì¾Ãæ¤Î¹àÌܤ˥ǥ£¥ì¥¯¥È¥ê¤Ç¤Ï¤Ê¤¤¤â¤Î¤¬Æþ¤Ã¤Æ¤¤¤ë¡£
.TP
.B EPERM
.\" This happens for at least MSDOS and VFAT file systems
.\" on kernel 2.6.13
.\"O The underlying file system does not support extending
.\"O a file beyond its current size.
²¼Áؤˤ¢¤ë¥Õ¥¡¥¤¥ë¥·¥¹¥Æ¥à¤Ç¤Ï¡¢¸½ºß¤Î¥Õ¥¡¥¤¥ëŤò±Û¤¨¤Æ
¥Õ¥¡¥¤¥ë¤ò¿­Ä¹¤¹¤ë¤³¤È¤¬¤Ç¤­¤Ê¤¤¡£
.TP
.B EROFS
.\"O The named file resides on a read-only file system.
»ØÄꤵ¤ì¤¿¥Õ¥¡¥¤¥ë¤ÏÆɤ߽Ф·ÀìÍѤΥե¡¥¤¥ë¥·¥¹¥Æ¥àÃæ¤Ë¤¢¤ë¡£
.TP
.B ETXTBSY
.\"O The file is a pure procedure (shared text) file that is being executed.
»ØÄꤵ¤ì¤¿¥Õ¥¡¥¤¥ë¤Ï¼Â¹Ô¤µ¤ì¤Æ¤¤¤ë¥Õ¥¡¥¤¥ë¤Ç¤¢¤ë¡£
.PP
.\"O For
.\"O .BR ftruncate ()
.\"O the same errors apply, but instead of things that can be wrong with
.\"O .IR path ,
.\"O we now have things that can be wrong with the file descriptor,
.\"O .IR fd :
.BR ftruncate  ()
¤Ë¤âƱÍͤΥ¨¥é¡¼¤¬Å¬ÍѤµ¤ì¤ë¡£
⤷¡¢
.I path
¤Ë´Ø¤¹¤ë¥¨¥é¡¼¤Î¾ì¹ç¤Ï¡¢¥Õ¥¡¥¤¥ë¥Ç¥£¥¹¥¯¥ê¥×¥¿¡¼
.I fd
¤Ë´Ø¤¹¤ë¥¨¥é¡¼¤È¤Ê¤ë¡£
.TP
.B EBADF
.\"O .I fd
.\"O is not a valid descriptor.
.I fd
¤¬Ìµ¸ú¤Ê¥Ç¥£¥¹¥¯¥ê¥×¥¿¡¼¤Ç¤¢¤ë¡£
.TP
.\"O .BR EBADF " or " EINVAL
.BR EBADF " ¤Þ¤¿¤Ï " EINVAL
.\"O .I fd
.\"O is not open for writing.
.I fd
¤Ç»ØÄꤵ¤ì¤Æ¤¤¤ë¤â¤Î¤¬½ñ¤­¹þ¤ß¥â¡¼¥É¤Ç³«¤«¤ì¤Æ¤¤¤Ê¤¤¡£
.TP
.B EINVAL
.\"O .I fd
.\"O does not reference a regular file.
.I fd
¤¬Ä̾ï¤Î¥Õ¥¡¥¤¥ë¤ò»²¾È¤·¤Æ¤¤¤Ê¤¤¡£
.\"O .SH "CONFORMING TO"
.SH ½àµò
.\"O 4.4BSD, SVr4, POSIX.1-2001 (these calls first appeared in 4.2BSD).
4.4BSD, SVr4, POSIX.1-2001 (¤³¤ì¤é¤Î¥³¡¼¥ë¤Ï 4.2BSD ¤Ç½é¤á¤ÆÅо줷¤¿)¡£
.\"O .\" POSIX 1003.1-1996 has
.\"O .\" .BR ftruncate ().
.\"O .\" POSIX.1-2001 also has
.\"O .\" .BR truncate (),
.\"O .\" as an XSI extension.
.\"O .\" .LP
.\"O .\" SVr4 documents additional
.\"O .\" .BR truncate ()
.\"O .\" error conditions EMFILE, EMULTIHP, ENFILE, ENOLINK.  SVr4 documents for
.\"O .\" .BR ftruncate ()
.\"O .\" an additional EAGAIN error condition.
.\" POSIX 1003.1-1996 ¤Ë¤Ï
.\" .BR ftruncate ()
.\" ¤¬¤¢¤ë¡£
.\" POSIX.1-2001 ¤Ë¤Ï
.\" XSI ³ÈÄ¥¤È¤·¤Æ
.\" .BR truncate ()
.\" ¤â¤¢¤ë¡£
.\" .LP
.\" SVr4 ¤Ë¤Ï¾¤Î¥¨¥é¡¼¥³¡¼¥É¤È¤·¤Æ¡¢
.\" .BR truncate ()
.\" ¤Ë¤Ï EMFILE, EMULTIHP, ENFILE, ENOLINK ¤¬¡¢
.\" .BR ftruncate ()
.\" ¤Ë¤Ï EAGAIN ¤¬¤½¤ì¤¾¤ìµ­½Ò¤µ¤ì¤Æ¤¤¤ë¡£
.\"O .SH NOTES
.SH Ãí°Õ
.\"O The above description is for XSI-compliant systems.
.\"O For non-XSI-compliant systems, the POSIX standard allows
.\"O two behaviors for
.\"O .BR ftruncate ()
.\"O when
.\"O .I length
.\"O exceeds the file length
.\"O (note that
.\"O .BR truncate ()
.\"O is not specified at all in such an environment):
.\"O either returning an error, or extending the file.
¾åµ­¤Îµ­½Ò¤Ï XSI ½àµò¤Î¥·¥¹¥Æ¥à¤Î¤â¤Î¤Ç¤¢¤ë¡£
XSI Èó½àµò¤Î¥·¥¹¥Æ¥à¤Î¾ì¹ç¡¢POSIX ɸ½à¤Ï
.BR ftruncate ()
¤ËÂФ·¤Æ
.I length
¤¬¥Õ¥¡¥¤¥ë¤ÎŤµ¤è¤êŤ«¤Ã¤¿¾ì¹ç¡¢
¥¨¥é¡¼¤òÊÖ¤¹¤«¥Õ¥¡¥¤¥ë¤ò¿­Ä¥¤¹¤ë¤«¤ÎÆó¤Ä¤ÎÆ°ºî¤òµöÍƤ·¤Æ¤¤¤ë¡£
.BR truncate ()
¤ËÂФ·¤Æ¤ÏÁ´¤¯µ¬Äꤵ¤ì¤Æ¤¤¤Ê¤¤¡£
.\"O Like most Unix implementations, Linux follows the XSI requirement
.\"O when dealing with native file systems.
.\"O However, some nonnative file systems do not permit
.\"O .BR truncate ()
.\"O and
.\"O .BR ftruncate ()
.\"O to be used to extend a file beyond its current length:
.\"O a notable example on Linux is VFAT.
¤Û¤È¤ó¤É¤Î Unix ¼ÂÁõ¤ÈƱÍÍ¡¢Linux ¤Ï¥Í¥¤¥Æ¥£¥Ö (Linux ͳÍè) ¤Î
¥Õ¥¡¥¤¥ë¥·¥¹¥Æ¥à¤Î°·¤¤¤Ç¤Ï XSI Í×µá»ÅÍͤˤ·¤¿¤¬¤Ã¤Æ¤¤¤ë¡£
¤·¤«¤·¤Ê¤¬¤é¡¢¤¤¤¯¤Ä¤«¤ÎÈó¥Í¥¤¥Æ¥£¥Ö¤Î¥Õ¥¡¥¤¥ë¥·¥¹¥Æ¥à¤Ç¤Ï¡¢
.BR truncate ()
¤ä
.BR ftruncate ()
¤ò»È¤Ã¤Æ¸½ºß¤Î¥Õ¥¡¥¤¥ëŤò±Û¤¨¤Æ¥Õ¥¡¥¤¥ë¤ò¿­Ä¹¤¹¤ë¤³¤È¤¬¤Ç¤­¤Ê¤¤¡£
Linux ¤Ç¤Îͭ̾¤ÊÎã¤È¤·¤Æ¤Ï VFAT ¤¬¤¢¤ë¡£
.\"O .\" At the very least: OSF/1, Solaris 7, and FreeBSD conform, mtk, Jan 2002
.\"O .SH "SEE ALSO"
.SH ´ØÏ¢¹àÌÜ
.BR open (2),
.BR stat (2),
.BR path_resolution (7)